The mysteries of specific mechanisms underlying Alzheimer?s Disease (AD) and Alzheimer's-Disease-Related Dementias (ADRD) are still being solved, as is understanding individual differences in susceptibility to differential rates of age-related cognitive decline and brain pathology. Proposals about sources, functions, and mechanisms associated with so-called cognitive reserve are central to one prominent theory about differential susceptibility. Although there is considerable debate about the precise operationalization of cognitive reserve, theory and research suggests that individuals possessing greater amounts of cognitive reserve are better able to cope with higher levels of brain pathology or other neurological insult before reaching clinical thresholds of progressive dementia-related impairment. Implicit in this theory is the possibility that cognitive reserve might be a modifiable risk factor. Given this assumption, much social science and public health research has focused on identifying societal and behavioral factors that contribute to the accumulation of cognitive reserve and account for secular trends in the prevalence of dementia. Educational attainment and occupation are two factors consistently invoked as potential sources of cognitive reserve but important gaps remain in understanding what aspects of educational and occupational experience are important, why, and for whom. We propose to leverage two new opportunities in the Health and Retirement Study (HRS) to examine some of these gaps. First, in the initial cycle of the project, we developed a Life History Mail Study (LHMS). The LHMS (fielded in 2015 and 2017) provides important insight into the content, quality, and contexts of early and lifelong education together with characteristics of job histories. This detail considerably enhances the scope and richness of information about these two factors and opens possibilities to link to historical administrative data. To date, most population research on older adults has been restricted to limited information about the number of years of early-life education and highest degree, and the characteristics of the last or longest job. In addition to the content and characteristics of education and jobs, the new LHMS data provide important information about lifetime exposures and trajectories (e.g., lifelong education, career progression, changes in job complexity, and trajectory disruptions). Second, in 2016, as part of a Healthy Cognitive Aging Project (HCAP), HRS introduced a new cognitive battery designed to identify progressive cognitive decline linked to ADRD after age 65. This extends the cognitive performance measures collected longitudinally in each HRS biennial wave. We will take advantage of this opportunity to examine hypotheses about the contributions of educational and occupational histories to differential late-life cognitive decline and dementia. To complete our analyses and continue to enhance the public-use HRS life history information, we will: i) consolidate LHMS data collected in various HRS waves; ii) collect the LHMS from the late baby boomer cohort; iii) enhance efforts to collect the LHMS from non-respondents; and iv) add codes for education and job qualities to the public files.